Microencapsulation is a process used to enclose volatile or chemically reactive compounds in starch microspheres so that long-term toxicity feeding studies can be conducted and to overcome potential palatability problems. Studies with microencapsulated citral in feed were compared with chemical administration by gavage in both sexes of F344 rats and B6C3F1 mice. Palatability was unaffected and toxic responses such as body and organ weight and tissue lesions occurred in the rodents, irrespective of route of exposure, indicating that microencapsulation could be used to replace the most costly and less desirable route of gavage administration in long-term studies. Higher doses of citral could be utilized after microencapsulation, resulting in maximization of the detection of potential toxic or carcinogenic responses. Further short-term toxicity studies to compare microencapsulated cinnamaldehyde, a volatile chemical, with chemical administration by gavage, are underway in both sexes of F344 rats and B6C3F1 mice. These studies will be used to determine target organ toxicity, and to select doses for longer-term studies by feeding the microencapsulated chemical, presuming this preferred route of administration can be utilized.